Speech Debelle told her producer Wayne "Lotek Hifi" Bennett to make her sound like a "hip-hop Tracy Chapman". For better and worse he succeeded. The 26-year-old south Londoner's debut Speech Therapy is a rap album rooted in the genre's respectable, conscious traditions – the lineage typified in the 1990s by A Tribe Called Quest, Mos Def, Common and Arrested Development.

The results, complete with tastefully applied cello and brass, could be damned as slightly worthy – "not black enough," as Debelle wearily guessed the reasoning must have gone behind closed doors, when London hip-hop station Choice FM wouldn't play her music. The irony of such first impressions – that the album is a little safe, approachable, suburban – becomes obvious when you listen to Debelle's words. The first line to cause neck-cricking double-takes at your speakers is from "Searching": "I know the blair witch I seen her yesterday, she collapsed naked in her bed with her needle in her crotches." The source of such visions, and stories elsewhere of searching for a female rival, knife in hand, come from Debelle's now well-documented three years living in hostels and dabbling in crime. The lyrics are understated, even when recalling abysses from which she might not have stepped back: "They say misery loves company and I'm so comfy I could fall asleep..." And not wake up, goes the unspoken next line, or ever surfaced to record a word.

Though lacking a great album, this year's Mercury shortlist had its share of confessional and confrontational artists, typified by Florence + the Machine's sexual battery fantasia "Kiss With a Fist". The Machine's Florence Welch, Bat for Lashes' Natasha Khan and Glasvegas's James Allan are also all nominees whose artistry flared partly because of an absent parent, and it's Allan, not the list's much-touted multitude of women, who is Debelle's truest soul-mate. Glasvegas's "Daddy's Gone" has its twin in Debelle's "Daddy's Little Girl" – both ruthless lancings of life-long, heart-deep pains. Debelle's lyrics are more detailed and retaliatory, imagining her absconding father grey, old, used-up and pathetic. It's fair exchange for an emotional hole that means, as she raps, "I'm affected anytime anybody leaves." It's a song of generational relevance.

Speech Debelle looked ecstatic receiving her Mercury Prize last night. But history suggests long-term success may be a struggle. Just ask 2002 winner Ms Dynamite – articulate, challenging, pop-savvy, and unceremoniously pointed to the knacker's yard with her second album. Most Mercury winners who have arrived out of the blue (Talvin Singh, Gomez, Roni Size, Antony and the Johnsons) have struggled to replicate their success. Debelle's uncommercial formula – "too black" or "not black enough", depending which side of the moronic musical ghetto you look over – won't help. What shouldn't be underestimated is her iron will and tough artistry. "I've gotta smooth my edges/ eat more veggies," as she pep-talks herself on Speech Therapy. Her grim experiences are her art's fuel, not its whole story. She has a voice which, in a fair world, we'll hear again.